This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-093961, filed Mar. 31, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a control device to average gain, especially, to a control device which averages gain of the radio repeater device in communication field.
Usually, the carrier amplifiers of up-link and down-link incorporated into the radio repeater device can obtain the amplification gain set for the input level. However, when the extremely high level signal is input, this amplifier has the disadvantage of saturating for the high sensitivity amplifier.
Thus, there is a disadvantage of generating the high frequency distortion when the amplifier is saturated because of the input of a high-level signal in the radio repeater device.
As described above, in the radio repeater device, the amplifier is saturated because of the input of a high-level signal, as a result, the high frequency distortion is occurred.
Since the radio repeater device treats a plurality of carriers, it is necessary to build in the I/O level limitation device not to occur the above-mentioned high frequency distortion.
An object of the present invention is to provide an effective control device to average gain, especially, to a control device which averages gain of amplifier device which operates at high frequency like radio repeater device in communication field.
The present invention adopts the following means to solve the above-mentioned problem.
A control device according to the present invention characterized by comprising: an input section which inputs a predetermined signal; an amplification section of a variable gain type which amplifies the predetermined signal; and a feedback loop which inputs a signal output from the amplification section and adjusts a gain of the amplification section to keep the output signal constant. The level of the input signal can be averaged, for example, in the radio repeater device since this feedback loop is provided. In the above-mentioned configuration, the band-pass filter may be omitted, when it is unnecessary to limit the frequency, and the number of stages of amplifier sections may be also arbitrary.
In the above-mentioned control device, the amplification section comprises an amplifier of a fixed-gain type and an attenuator in which an attenuation amount is changed according to a signal from the feedback loop. Since the amplifier and the attenuator is provided and the adjustment of the gain is performed with the attenuator, the operation of the amplifier becomes stable in addition to the above-mentioned advantage.
In the above-mentioned control device, the attenuator has an attenuation element including a PIN diode, a first resistance element having a first end and a second end, the first end connected with a previous stage of the attenuation element and the second end connected with a first voltage, and a second resistance element having a third end and a fourth end, the third end connected with a previous stage of the attenuation element and the fourth end connected with a second voltage. Since high-speed operation becomes possible by using the element which can perform high-speed switching like the PIN diode as an attenuation element of the attenuator, a suitable control device for the radio repeater device especially used in the high frequency region can be provided in addition to the above-mentioned advantage.
In the above-mentioned control device, the amplification section comprises at least a first amplifier and a second amplifier of a variable gain type, the device further comprises a band-pass filter arranged between the first amplifier and the second amplifier to pass only a signal of a predetermined band, and the first amplifier amplifies the input signal to output an amplified signal to the band-pass filter, and the second amplifier amplifies a signal which has passed the band-pass filter. Averaging the level of the input signal in the radio repeater device becomes possible with such a configuration.
The control device according to the present invention characterized by comprising: an antenna which receives a carrier; a first amplification section of a variable gain type which amplifies the carrier; a band-pass filter to pass only a carrier in a predetermined band; a second amplification section of a variable gain type which amplifies a carrier which has passed the band-pass filter; and a feedback loop which inputs a carrier output from the second amplification section and adjusts a gain of the first and the second amplification sections to keep the output carrier constant. Averaging the level of the input signal in the radio repeater device becomes possible with such a configuration.
The control device according to the present invention is characterized by comprising: an antenna which receives a division multiplexed carrier; a first band-pass filter to pass a desired band of the carrier; a plurality of amplifiers provided in each channel which amplifies a carrier, which has passed the first band-pass filter, to a desired intensity for each channel; a scanning section which phase-synchronizes the carrier which has passed the first band-pass filter, performs analog-to-digital conversion of a detected signal and output a converted signal; and a controller which sets an optimal output of the plurality of amplifiers based on the signal from the scanning section and adjusts gains of the plurality of amplifiers. Averaging the level of each channel in the division multiple access method is possible.
As described above, an effective input signal level can be averaged with a simple circuit. Especially, it is possible to average the input signal in the high frequency region. It is possible to apply to the control circuit (device) which keeps a variety of physical amount to be constant with a simple circuit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.